Railroad Vehicle Control Device Insulation Strategy
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Solution Overview
Problem
The existing railroad vehicle driving device faces issues with unintentional electrical contact between high and low voltage circuits due to a voltage drop during internal combustion engine startup, which can negatively affect the control device, especially when the internal combustion engine lacks a starter and relies on a power storage means with low voltage.
Innovation Solution
A railroad vehicle control device is designed with a first power conversion device, a smoothing capacitor, a second power conversion device, a first power storage device, and a controller, where the second power conversion device insulates its input and output sides, and a first contactor switches between the smoothing capacitor and the power storage device to prevent electrical contact, ensuring safe power supply to the generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power storage means is directly connected to the smoothing capacitor to charge it, then the power storage means can supply electric power to the control device, but unintentional electrical contact between high voltage circuit and low voltage circuit may occur
Solution Approach 1:
The patent introduces a second power conversion device as an intermediary between the power storage means (low voltage circuit) and the smoothing capacitor (high voltage circuit). This device includes an insulating transformer that provides galvanic isolation, preventing direct electrical contact while enabling power transfer. The insulating transformer acts as a mediator that transfers energy without creating a direct conductive path between the two circuits.
Solution Approach 2:
The patent segments the power conversion system into distinct functional modules: a first power conversion device for AC-DC conversion, a second power conversion device for DC-DC conversion with insulation, and a contactor for circuit isolation. This segmentation allows each module to perform its specific function while maintaining electrical insulation boundaries, particularly through the isolated DC-DC converter that separates high and low voltage domains.
2Adaptability or versatility
If the power storage means with low voltage is used to start the internal combustion engine, then the engine can be started without a starter, but the internal resistance causes considerable temporary drop in terminal voltage affecting the control device
Solution Approach 1:
The insulating transformer in the second power conversion device serves as an intermediary that isolates the control device from voltage fluctuations in the power storage means. During engine starting when large currents are drawn causing voltage drops, the transformer's magnetic coupling transfers energy while blocking the propagation of voltage transients to the control device side, thus protecting control device operation.
Solution Approach 2:
The patent provides beforehand cushioning by introducing the insulating transformer and associated filtering components that cushion against voltage drops during engine starting. The transformer's inductance and the circuit design absorb and smooth out the temporary voltage drops caused by high starting currents, preventing them from reaching the control device and causing malfunctions.
3Adaptability or versatility
If the contactor is used to switch between charging and power generation modes, then the system can flexibly control power flow, but the contactor may stick or be wrongly closed causing insulation failure
Solution Approach 1:
The insulating transformer acts as a permanent intermediary that maintains electrical insulation regardless of contactor position. Even if the contactor sticks or is wrongly closed, the transformer's galvanic isolation ensures that high voltage cannot directly contact the low voltage circuit through the power storage means, providing inherent safety against contactor failures.
Solution Approach 2:
The patent provides beforehand cushioning against contactor failure by designing the system with inherent insulation through the transformer. This pre-established insulation barrier cushions against the potential harmful effects of contactor sticking or wrong closure, ensuring that even in failure modes, the electrical insulation between high and low voltage circuits is maintained.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents unintentional electrical contact between high and low voltage circuits, stabilizes the voltage during engine startup, and reduces the risk of voltage drops affecting the control device, ensuring reliable operation.
Implementation Method 1
a first power conversion device, a primary side of which is connected to a power generator driven by an internal combustion engine to generate alternating current, and which performs bidirectional power conversion between the primary side and a secondary side of the first power conversion device
Implementation Method 2
a smoothing capacitor connected to terminals of the secondary side of the first power conversion device
Implementation Method 3
a second power conversion device which converts electric power supplied from a power source connected to an input side of the second power conversion device and then outputs the converted electric power, wherein input and output sides of the second power conversion device are insulated from each other
Implementation Method 4
a first contactor which switches on and off an electrical pathway located between the smoothing capacitor and the first power storage device
Implementation Method 5
the controller controls the first power conversion device after the smoothing capacitor is charged by supplying to the smoothing capacitor electric power stored in the first power storage device by closing the first contactor, so that the first power conversion device converts electric power stored in the smoothing capacitor and supplies the converted electric power as electric power for driving the power generator
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A second power conversion device (17) converts electric power supplied from a power source connected to an input side of the second power conversion device (17), to supply the converted electric power to a first power storage device (16). A first contactor (15) is closed, such that a smoothing capacitor (12) is charged with electric power stored in the first power storage device (16). A controller (18) controls a first power conversion device (11) to cause the first power conversion device (11) to perform power conversion of electric power stored in the smoothing capacitor (12) and to supply the converted electric power to a power generator (3).